RESEARCH Open Access

Public sentiments towards the use ofWolbachia-Aedes technology in SingaporeChristina Liew1,2*, Li Ting Soh1, Irene Chen1 and Lee Ching Ng1,2

Abstract

Background: Wolbachia technology is a novel vector control approach that can reduce mosquito populations andthe risk of mosquito-borne diseases, which has recently gained popularity amongst countries. In 2016, Singaporeembarked on a multi-phased field study named Project Wolbachia – Singapore, to evaluate the use of Wolbachiatechnology as an Aedes aegypti mosquito population suppression tool to fight dengue. Due to the novelty of thistechnology in Singapore, this study aims to understand the public’s acceptance and sentiments towards the use ofWolbachia technology.

Methods: Several public sentiment survey approaches – including online, face-to-face in the streets, as well asdoor-to-door household surveys – were conducted.

Results: The surveys conducted prior to the first field releases and implementation of the project revealed highsupport for the use of Wolbachia technology in Singapore. A household perception survey conducted in theinterim of the first project phase was encouraging, with the majority of the respondents being aware of the projectand having no concerns with the release of male Wolbachia-carrying Aedes aegypti (Wolbachia-Aedes) mosquitoes intheir neighbourhood.

Conclusions: The study reveal high support for the use of Wolbachia technology in Singapore and also providedinvaluable insights that were used in the development of a public communications and engagement frameworkmodel, which thus helped to guide these elements in the subsequent phases and expansion of the project.

Keywords: Wolbachia, Perception, Survey, Dengue, Singapore

BackgroundThe use of Wolbachia strategy to suppress vector popu-lations is a novel approach, which has the potential toreduce mosquito populations and the risk of mosquito-borne disease transmission [1, 2]. This approach, com-monly known as the Incompatible Insect Technique(IIT), is a species-specific and benign approach for con-trolling vector populations [3]. Eggs produced from thesuccessful mating between released male Wolbachia-car-rying Aedes aegypti (Wolbachia-Aedes) mosquitoes and

urban female Aedes aegypti mosquitoes in the environ-ment (without Wolbachia) are non-viable, due to Cyto-plasmic Incompatibility (CI), therefore suppression ofmosquito populations could be achieved with regular re-leases over time [3, 4].Field studies are necessary to demonstrate that the

male Wolbachia-Aedes mosquitoes behave in the sameway as they do in the laboratory, when subjected to en-vironmental conditions in the field. The potential ofusing this strategy was first demonstrated in the sup-pression of Culex pipiens in Myanmar [5]. Improvedtechnology in recent years made the microinjection ofWolbachia strains into mosquito species possible [6],allowing exploitation of the Wolbachia strategy for sup-pressing populations of mosquito species [7–9].

© The Author(s). 2021 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License,which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you giveappropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate ifchanges were made. The images or other third party material in this article are included in the article's Creative Commonslicence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commonslicence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtainpermission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to thedata made available in this article, unless otherwise stated in a credit line to the data.

* Correspondence: christina_liew@nea.gov.sg1Environmental Health Institute, National Environment Agency, Singapore,Singapore2School of Biological Sciences, Nanyang Technological University, Singapore,Singapore

Liew et al. BMC Public Health (2021) 21:1417 https://doi.org/10.1186/s12889-021-11380-w

Numerous field trials have been reported recently, in-cluding successful population suppression of the Poly-nesian tiger mosquito, Aedes polynesiensis, in FrenchPolynesia [10]; Aedes albopictus in China [11–13] and inthe United States [14]; and Aedes aegypti in the UnitedStates [15], in Australia [16], as well as in Thailand [17].To test the effectiveness of the Wolbachia-Aedes sup-pression approach, a multi-phased field study – named‘Project Wolbachia – Singapore’ – was launched in 2016by the National Environment Agency (NEA), a statutoryboard under the Ministry of Sustainability and the Envir-onment (MSE) [previously known as the Ministry of theEnvironment and Water Resources, MEWR], Govern-ment of Singapore. This population suppression ap-proach involves the release of male Wolbachia-Aedesmosquitoes in a high-rise and densely built urbanenvironment.Many such field trials acknowledge the complexities

and challenges that come with politics and ethics, hencethe importance of both community and governmentsupport are emphasised, in addition to high scientificquality [18]. With public consultations and engagementdeemed critical for successful implementation of theWolbachia-Aedes technology, several authors have rec-ommended strategies for effective community engage-ment [18–22]. These strategies include understandingthe socio-political context of the local population, closeengagement with local communities informing them ofthe study, and periodic update of the project [16, 23].In Singapore, extensive stakeholder engagement re-

garding the use of the Wolbachia-Aedes suppression ap-proach was planned and put in place, prior to anypossible field releases [24]. Early consultations with keyrelevant stakeholder groups – such as local and inter-national academia, scientists, medical doctors, the localnature society, specific interest groups, communityleaders, and residents at the selected study sites –allowed the identification of risks and understanding ofcommunity concerns, to help shape key public commu-nications messaging and gain early support from theseimportant groups. During project implementation, de-tailed information and timely updates were regularlyprovided through various channels, including: publicitybanners and posters placed at strategic locations withhigh footfall at the study sites; educational brochuresprepared in Singapore’s four official languages (English,Mandarin, Malay and Tamil) distributed to every singlehousehold/ other premises within the study sites; andregular, detailed informational updates provided viamainstream (print and online) media, social media, aswell as NEA’s Project Wolbachia – Singapore webpage.Besides the dissemination of information, Learning Jour-neys to NEA’s Mosquito Production Facility, sharing ses-sions at schools and childcare centres, and mass

outreach sessions via roadshows for the general public,were regularly conducted face-to-face, to generateawareness and understanding. Another key aspect ofSingapore’s engagement strategy was ensuring a trans-parent and responsive feedback system to address con-cerns in the community – including via telephonehotline, email, an online reporting system, and verbalfeedback to NEA field officers on the ground – whichwere crucial for maintaining trust with, and accountabil-ity to, our stakeholders.Enhanced community engagement for the understand-

ing of Wolbachia technology does not necessarily equateto public approval and acceptance. In several field stud-ies, an individual informed-consent approach wasadopted, and releases were done only at sites where au-thorisation was obtained from households in the com-munity [16, 25]. While this approach is plausible for asmall-scale field study, it is challenging for large-scaledeployment [26].To understand public acceptance and sentiments to-

wards the use of Wolbachia-Aedes technology inSingapore, we adopted several public sentiment surveyapproaches, including online, face-to-face in streets, aswell as door-to-door household surveys. Herein, we ex-amined the public’s awareness of dengue, and the pub-lic’s opinion towards the use of Wolbachia-Aedestechnology prior to the first field releases conducted inOctober 2016, as well as the perception of residents atthe study sites in the interim of the first project phase.The association of social-demographic characteristics,knowledge and attitude of the public towards the releaseof male Wolbachia-Aedes were analysed. The surveysconducted also served as one of the channels for ac-countability to residents and stakeholders, gatheringfeedback from the community, and addressing residents’concerns.

MethodsOnline public perception surveyAn independent consultancy firm was engaged to con-duct an online public perception survey, to gather publicperceptions and sentiments towards Project Wolbachia– Singapore, as part of our risk assessment on the use ofWolbachia technology. An email with an embedded linkto the online survey portal was sent to a database of sur-vey respondents, and the online survey portal wasopened for three weeks from May to June 2016.

Face-to-face street surveyA quick face-to-face street survey targeting the olderpopulation (aged above 40) was conducted over oneweekend in August 2016, to complement the online sur-vey results. The survey questionnaire captured demo-graphic variables, such as age, gender, highest education

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level, and the respondents’ knowledge on and sentimentstowards the use of Wolbachia technology. The surveywas conducted using the QuestionPro web-based plat-form (QuestionPro.com). Surveyors were trained beforeconducting the surveys, to ensure that the objectives,methodology, expectations and questionnaires were wellunderstood.

Household perception surveyHousehold perception surveys were administered at allthree selected release sites, at Braddell Heights, (Releasesite 1_BH), Tampines West (Release site 2_TW) andNee Soon East (Release site 3_NSE), during the first twomonths of the small-scale field study, carried out fromNovember to December 2016. The survey was con-ducted using the same structured questionnaire that wasused in the face-to-face street survey interviews. Sur-veyors were trained before conducting the surveys, toensure that the objectives, methodology, expectationsand questionnaires were well understood.

Household perception survey at release site 1_BHRelease site 1_BH was a landed estate with private resi-dential houses. Using the location map of the estate, sur-veyors approached residents of all the residential housesto conduct the household perception survey. One re-spondent from each household was interviewed, afterobtaining his/her informed consent to participate. In theevent of any of the following scenarios: (i) no respondentpresent at the household; (ii) respondent refused to par-ticipate; or (iii) unable to communicate with the re-spondent, the surveyor noted the response andproceeded to the next household in a systematic man-ner. Household responses that were recorded under sce-nario (i) on the first occasion were re-visited (up to twotimes) on different days and timings, in order to tryobtaining a response. A total of 113 perception surveywere collected at Release site 1_BH.

Household perception survey at release site 2_TW andrelease site 3_NSERelease site 2_TW and Release site 3_NSE were residen-tial estates with blocks of public housing flats, managedby the Housing & Development Board (HDB) ofSingapore. Based on the household estimates at Releasesite 2_TW and Release site 3_NSE, the minimum surveysample size was calculated using Epi Info™ version 7.2(Centers for Disease Control, Atlanta, US), using the fol-lowing parameters: 5% confidence limits and 95% confi-dence level as shown in Table 1. The expected frequencyof the outcome was considered at 50%, because thestudy covers several potential variables. Based on theminimum survey sample size, a representative numberof surveys was conducted at each residential block at the

study sites. A randomised household list was generatedfor each block, and door-to-door surveys were con-ducted for the randomised household list. One respond-ent from each household was interviewed, afterobtaining his/her informed consent to participate. In theevent of any of the following scenarios: i) no respondentpresent at the household; ii) respondent refused to par-ticipate; or iii) unable to communicate with the respond-ent, the next household in the list was invited toparticipate, until the minimum sample size required wasreached.

ResultsOnline public perception surveyA total of 1012 respondents participated in the onlinepublic perception survey. Comparing the survey popula-tion with the Singapore population figures in 2015,reflected in the Yearbook of Statistics 2016 [27] and theGeneral Household Survey of 2015 [28], the survey re-sults obtained over-represented younger and more edu-cated respondents. As such, the analysis for respondentsaged 40 years and above were excluded in this section,and the analysis was focused on younger respondentswho were representative of the population, aged from 20to 39 years (within about 5% of the population, as mea-sured in 2015). Various adjustments were made to allowfor a comparison, including merging groups, assuminguniform distributions of age categories, and mappingdefinitions of variables between data sets. The demo-graphic profile of survey respondents is summarised inTable 2.Survey responses were analysed, and the questions on:

i) how comfortable participants are with the use of Wol-bachia technology at a dengue hotspot near their homes;ii) how confident they are with Wolbachia technology;and iii) if they think the Government should use Wolba-chia technology, were found to be highly correlated(Chronbach’s alpha ≈0.76). Hence in this paper, we fo-cused our analysis on whether the survey respondentsthought the government should implement Wolbachiatechnology in relation to their demographic background.In general, 97% of the population (aged from 18 to 39

years) did not oppose the implementation of Wolbachiatechnology in Singapore. Analysis of the results foundstrong agreement with the Government’s implementa-tion of Wolbachia technology (18% strongly agreed, 51%agreed, and only 3% disagreed or strongly disagreed).

Table 1 Sample size for survey conducted in Release site 2_TWand Release site 3_NSE

Selected sites Household estimates Survey sample size(minimum sample size)

Release site 2_TW 2941 382 (340)

Release site 3_NSE 1000 281 (278)

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This agreement on implementation of Wolbachia tech-nology was fairly consistent across all demographicgroups considered. No significant difference in the sup-port for use of Wolbachia technology was found amongrespondents of different age groups. However, a signifi-cant difference was observed among respondents of dif-ferent genders and educational background. Comparedto female respondents, men were less hesitant about thenew technology, and more men were in favour of it (p =0.00187). Compared to respondents with tertiary educa-tion, respondents with primary school level or lowereducation background were more inclined to be neutralor to disagree with the implementation of Wolbachiatechnology (p = 0.02). However in this study, the numberof respondents (aged from 18 to 39 years) with primaryschool or lower education background was relativelysmall (n = 5), therefore estimates on the support for useof Wolbachia technology from this group of respondentswere not reliable.Further analysis was also done to assess other attitudes

or knowledge that may have contributed to the respon-dents’ attitudes towards the use of Wolbachia technol-ogy, in particular their impression of the severity of thedengue situation in Singapore, approval of the Govern-ment’s approach to control dengue, and general

knowledge of dengue. Results of the analysis are sum-marised in Table 3.

Impression of the severity of the dengue situation inSingaporeRespondents’ impressions of the severity of the denguesituation in Singapore were categorised into threegroups: (1) those who were unsure or did not feel thatdengue is serious; (2) those who felt that dengue wasserious but was under control; and (3) those who feltthat dengue was serious and required action. A largerproportion of negative attitudes towards the use of Wol-bachia technology was found among respondents in thecategory who expressed being unsure and generally didnot feel that dengue is a serious problem (p = 0.003),compared to those in the other categories. However, it isnoted that most individuals in this group were still sup-portive of the use of Wolbachia technology.

Approval of the Government’s approach to controllingdengueRespondents’ responses were split into two categories:(1) those who approved, and (2) those who disapprovedof the Government’s efforts in controlling dengue. Re-spondents who disagreed with the use of Wolbachia

Table 2 Demographic profile of survey respondents who participated in the online perception survey

Categories RespondentDistribution (%)

Population %(From the Yearbook of Statistics 2016and the General Household Survey of 2015)

Adjusted RespondentDistribution (%)After exclusion ofpopulation > 40

AdjustedPopulation %

Gender

Male 44% 49% 44% 51%

Female 56% 51% 56% 49%

Age (years)

≤18 0% * 0% *

18–24 22% 12% 29% 30%

25–29 18% 9% 24% 22%

30–34 20% 9% 26% 24%

35–39 15% 10% 20% 25%

40–44 11% 10% 0% *

45–55 11% 22% 0% *

>55 3% 30% 0% *

Education Level

PSLE or none 1% 19% 1% 2%

‘O’-Levels orequivalent

12% 8% 10% 14%

‘A’-Levels orequivalent

7% 18% 7% 13%

Diploma 27% 27% 28% 18%

Degree or further 53% 27% 54% 53%

* Excluded for comparison; sum for other ages scaled to 100%

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technology were mostly from category (2), who thoughtthat the Government’s efforts were inadequate (p =0.003).

Knowledge of dengueRespondents were divided into three groups (high know-ledge of dengue, moderate knowledge of dengue, andlow knowledge of dengue), based on their answers to thefollowing four dichotomous True/False questions aboutdengue infection.

1. Only female mosquitoes bite. Male mosquitoes do not bite.2. Aedes aegypti, the main mosquito transmitter of dengue in Singapore,is more commonly found in urban areas than in forested areas.3. There is currently no cure for dengue.4. Dengue is only transmitted through mosquito bites.

No association was found between respondents’knowledge of dengue and their support for the use ofWolbachia technology.

To better understand the areas of concern that thepublic may have on the use of Wolbachia technology,respondents were tasked to rank the top three highestconcerns below:

1. Negative impact on the ecosystem2. Increase in mosquitoes in the environment3. Negative effects of Wolbachia on human health4. Irritation/anxiety due to increase in mosquitoes5. Doubts about the effectiveness of Wolbachia technology in controllingdengue6. Unknown side effects of Wolbachia (e.g. mutation of mosquitoes)7. Increase in my overall expenditure on controlling dengue8. Government/authorities will have to spend more on controllingincreased populations of mosquitoes

The top three concerns amongst the respondentswere: the unknown side effects of Wolbachia (33%);unspecified negative impact on human health (26%); andimpact on the ecosystem (25%). Additional costs(incurred by individuals or the Government) were rarely

Table 3 Analysis of respondents’ attitude or knowledge that may have contributed to their attitude towards the use of Wolbachiatechnology

Attitude/knowledge Should Wolbachia technology be implemented? Analysis ofresults

Impression of dengue situation Significant,p = 0.003

Approval of Government’s effortsin controlling dengue

Significant,p = 0.003

Knowledge of dengue Notsignificant

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mentioned as a concern, regarding the use of Wolbachiatechnology.In addition, respondents were asked about their

possible reaction, following the hypotheticalestablishment of a Wolbachia-Aedes suppressionprogramme. A significant proportion of respondents(81%) speculated that they would continue with theircurrent efforts to prevent mosquito breeding. A smallnumber of individuals stated that they would stopcurrent efforts to prevent mosquito breeding.

Face-to-face street surveyTwo groups (those aged over 40 years, and those whohad completed their education at primary or secondaryschool level) were substantially under-represented in theinitial online survey. Therefore a face-to-face street sur-vey targeting the older population (aged above 40) wasconducted, to complement the online survey results. Atotal of 163 respondents participated in the face-to-facestreet survey, with the demography of the respondentssummarised in Table 4.89% of the street survey respondents had no concern

(they either agreed or were neutral) with the release ofmale Wolbachia-Aedes mosquitoes in theirneighbourhood. In addition, 31% of the street surveyrespondents had heard of Project Wolbachia –Singapore.

Household perception surveyA total of 776 household perception surveys wereadministered at all three selected release sites –Releasesite 1_BH (N = 113), Release site 2_TW (N = 382), andRelease site 3_NSE(N = 281). As male Wolbachia-Aedesreleases at Release site 1_BH were conducted at a singlepoint in the landed estate while releases in Release site2_TW and Release site 3_NSE public housing estateswere conducted at multiple points on ground floors,analysis of Release site 1_BH was done separately fromRelease site 2_TW and Release site 3_NSE.

Release site 1_BHAt Release site 1_BH, 88% (n = 100) of the householdssurveyed had heard of Project Wolbachia – Singapore,and of the various outreach materials distributed andactivities conducted, the majority of households firstheard of the project through the news (32%), publicitymaterials (23%), door-to-door house visits conducted byproject officers (20%), and during the garden party orga-nised in the community prior to the first releases of maleWolbachia-Aedes mosquitoes (18%). 88% of the house-holds (n = 100) at Release site 1_BH, had no concernswith the release of male Wolbachia-Aedes mosquitoes intheir neighbourhood. However, a small concentration ofhouseholds near the release site (single point release)expressed that they were uncomfortable with the release.The socio-demographic factors of respondents, their

perception towards the Government’s efforts, and theirawareness of the dengue situation, were then analysed,to identify an attributing factor that may contribute to apositive outcome (comfortable/very comfortable withmale Wolbachia-Aedes release), as summarised inTable 5. Univariate analysis showed no association be-tween the socio-demography of respondents and theiracceptance towards male Wolbachia-Aedes release.Looking at the factors that may contribute to higherawareness of dengue (feels that dengue is a serious prob-lem/serious problem but under control), the odds of arespondent with a diploma/degree/postgraduate degree(compared to having a Primary School Leaving Examin-ation or PSLE certificate, and below) feeling that dengueis a serious problem/serious problem but under controlwas 5.14 times more likely.

Release site 2_TW and release site 3_NSEThe majority of the households surveyed at Release site2_TW (69%) and Release site 3_NSE (72%) had heard ofProject Wolbachia – Singapore, and of the variousoutreach materials distributed and activities conducted,most first heard of the project through the news(Release site 2_TW: 56%; Release site 3_NSE: 35%) andpublicity materials (Release site 2_TW: 24%; Release site3_NSE: 33%). At both sites, 92% of the households had

Table 4 Demographic profiles of respondents in the face-to-face street survey

Categories Respondent Distribution,N = 163 (n %)

Gender

Male 83 (51%)

Female 80 (49%)

Age (years)

≤ 20 0 (0%)

21–30 5 (3%)

31–40 4 (2%)

41–50 37 (23%)

51–60 52 (32%)

>60 65 (40%)

Education Level

PSLE and below 41 (25%)

‘O’-Level or equivalent 37 (23%)

‘A’-Level or equivalent 7 (4%)

Diploma 22 (13%)

Degree 34 (31%)

Postgraduate degree (MSc/PhD) 22 (13%)

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no concerns with the release of male Wolbachia-Aedesmosquitoes in their neighbourhoods.The socio-demographic factors of respondents from

Release site 2_TW and Release site 3_NSE, their percep-tion towards the Government’s efforts, and their aware-ness of the dengue situation, were analysed, to identifyan attributing factor that may contribute to a positiveoutcome (comfortable/very comfortable with maleWolbachia-Aedes release), as summarised in Tables 6, 7and 8.Using univariate analysis, the middle-age group (OR =

2.44, 95% CI = 1.75–3.41; p = 0.007) was found to be as-sociated with a positive attitude towards male Wolba-chia-Aedes release at Release site 2_TW. However, afurther Chi squared test showed no significant correl-ation (p = 0.063).Respondents with the perception of the Government’s

efforts in controlling dengue being adequate at bothRelease site 2_TW (OR = 2.37, 95% CI = 1.63–3.90; p =0.033) and Release site 3_NSE (OR = 3.74, 95% CI =2.25–6.22; p = 0.009) were also found to be associatedwith a positive attitude towards male Wolbachia-Aedes

release. A further Chi squared test done showedsignificant correlation between the impression ofadequate Government efforts and a positive attitudetowards male Wolbachia-Aedes release for both sites –Release site 2_TW (p = 4.91 × 10− 10) and Release site 3_NSE (p = 0.0009).Further multinomial regression analysis performed

found that the odds of a respondent who felt that theGovernment’s efforts were extremely adequate was 12times more likely to be very comfortable towards maleWolbachia-Aedes release, as shown in Table 7).Using univariate analysis, the older age group (OR =

0.41, 95% CI = 0.26–0.64; p = 0.04) was found to beassociated with a high awareness of dengue (feels thatdengue is a serious problem/serious problem but undercontrol) at Release site 3_NSE. However, a further Chisquared test showed no significant correlation (p = 0.06).Respondents at Release site 2_TW who had at least a

diploma tended to feel that dengue was a seriousproblem/serious problem but under control (OR = 6.15,95% CI = 3.54–10.7; p = 0.001); a further Chi squaredtest done showed significant correlation (p = 0.0003). At

Table 5 Analysis of socio-demographic factors of respondents at Release site 1_BH, their perception towards Government’s efforts,their awareness of the dengue situation, and their attitude towards Wolbachia release

Positive attitude towards male Wolbachia-Aedes release (very comfortable/comfortable)

High awareness of dengue (feels that dengue is aserious problem/serious problem but under control)

N n (%) Odds Ratio [95% CI] p-value N n (%) Odds Ratio [95% CI] p-value

Gender

Male 52 40 (77%) Reference 52 38 (73%) Reference

Female 61 39 (64%) 0.53 [0.35,0.81] 0.14 61 38 (62%) 0.61 [0.40, 0.92] 0.225

Age (years)

≤35 20 15 (75%) Reference 20 14 (70%) Reference

36–55 40 27 (68%) 0.69 [0.37,1.28] 0.55 40 33 (83%) 2.02 [1.06,3.84] 0.27

>55 53 37 (70%) 0.77 [0.42,1.40] 0.66 53 29 (55%) 0.52 [0.30,0.91] 0.24

Education level

PSLE and below 15 11 (73%) Reference 15 6 (40%) Reference

‘O’/ ‘A’ - Level or equivalent 36 23 (64%) 0.64 [0.33,1.27] 0.51 36 22 (61%) 2.36 [1.26,4.42] 0.17

Diploma/ Degree/ Postgraduatedegree

62 45 (73%) 0.96 [0.50,1.84] 0.95 62 48 (77%) 5.14 [2.80,9.45] 0.007

Perception towards Government’s efforts

Extremely inadequate/ Inadequate 12 7 (58%) Reference 12 11 (92%) Reference

Neutral 11 8 (73%) 1.90 [0.78,4.66] 0.47 11 4 (36%) 0.052 [0.015,0.18] 0.015

Adequate 68 46 (68%) 1.49 [0.79,2.83] 0.53 68 48 (71%) 0.22 [0.074,0.64] 0.16

Extremely adequate 22 18 (82%) 3.21 [1.44,7.19] 0.15 22 13 (59%) 0.13 [0.042,0.41] 0.073

Awareness of dengue situation

Not serious 22 13 (59%) Reference

Unsure 15 11 (73%) 1.90 [0.92,3.94] 0.38

Serious 21 17 (81%) 2.94 [1.45,5.95] 0.13

Serious but under control 55 38 (69%) 1.55 [0.92,2.61] 0.40

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Release site 3_NSE, respondents with ‘O’/‘A’ Levelqualifications tended to feel that dengue was a seriousproblem/serious problem but under control (OR = 4.30,95% CI = 2.50–7.05; p = 0.006); a further Chi squaredtest done showed significant correlation (p = 1.99 ×10− 5).Taking the survey response “dengue is not serious” as

the reference point for dengue awareness, and “PSLEand below” as the reference point for education level,the respondent’s education level and their awareness ofdengue was compared using multinomial regressionanalysis. In general, respondents at both release siteswith at least ‘O’/‘A’ Level qualifications tended to feelthat dengue was a serious problem/serious problem butunder control. The results are summarised in Table 9.

DiscussionUnderstanding the public’s concerns and sentimentsprovided invaluable insights on how to better engageresidents and stakeholders in the community, togenerate awareness and understanding of the Wolbachia

technology, and address any feedback and concerns.Results from the online survey conducted before thefirst releases and trialling implementation of theWolbachia technology in the small-scale field study, sug-gested that a small proportion of individuals may feelcomplacent and stop trying to prevent mosquito breed-ing with the implementation of Wolbachia technology[29, 30]. This led us to highlight the importance of con-tinued individual efforts in preventing mosquito breed-ing as one of the key messages, during extensivecommunity engagement efforts at the study sites beforethe first releases and small-scale field study began.From the survey data, we gleaned insights on the

awareness and attitudes towards dengue among theonline respondents in Singapore, as well as from theresidents living at specific study sites. About 88% of theonline survey respondents, and 68 to 77% of theresidents at the selected study sites (BH, TW and NSE),perceived dengue as a serious problem in Singapore.73% of the online survey respondents, and about 66 to80% of the residents at the selected study sites, felt that

Table 6 Analysis of socio-demographic factors of respondents at Release site 2_TW and Release site 3_NSE that attribute to positiveattitude towards male Wolbachia-Aedes release

Release site 2_TW Release site 3_NSE

Positive attitude towards male Wolbachia-Aedesrelease (very comfortable/comfortable)

Positive attitude towards male Wolbachia-Aedesrelease (very comfortable/comfortable)

N n (%) Odds Ratio[95% CI]

p-value N n (%) Odds Ratio[95% CI]

p-value

Gender

Male 176 134 (76%) Reference 109 90 (83%) Reference

Female 206 152 (74%) 0.88 [0.70,1.12] 0.60 172 131 (72%) 0.67 [0.49,0.91] 0.20

Age (years)

≤35 127 86 (68%) Reference 88 65 (74%) Reference

36–55 98 82 (84%) 2.44 [1.75,3.41] 0.007 86 70 (81%) 1.55 [1.07,2.24] 0.24

>55 157 118 (75%) 1.44 [1.11,1.88] 0.17 107 86 (80%) 1.45 [1.03,2.04] 0.28

Education level

PSLE and below 139 100 (72%) Reference 109 86 (79%) Reference

‘O’/ ‘A’ - Level or equivalent 132 108 (82%) 1.76 [1.31,2.36] 0.056 88 70 (80%) 1.04 [0.73,1.48] 0.91

Diploma/ Degree/ Postgraduate degree 111 78 (70%) 0.92 [0.70,1.22] 0.77 84 65 (77%) 0.91 [0.64,1.30] 0.80

Perception towards Government’s efforts

Extremely inadequate/ Inadequate 25 15 (60%) Reference 19 11 (58%) Reference

Neutral 53 31 (58%) 0.94 [0.57,1.54] 0.90 48 32 (67%) 1.45 [0.83,2.53] 0.50

Adequate 263 208 (79%) 2.52 [1.63,3.90] 0.033 172 144 (84%) 3.74 [2.25,6.22] 0.009

Extremely adequate 41 32 (78%) 2.37 [1.36,4.13] 0.12 42 34 (81%) 3.09 [1.68,5.68] 0.06

Awareness of dengue situation

Not serious 46 38 (83%) Reference 36 31 (86%) Reference

Unsure 41 24 (59%) 0.30 [0.18,0.49] 0.016 27 20 (74%) 0.46 [0.24,0.88] 0.23

Serious 77 54 (70%) 0.49 [0.31,0.78] 0.13 62 44 (71%) 0.39[0.23, 0.69]

0.09

Serious but under control 218 170 (78%) 0.75 [0.49,1.14] 0.49 156 126 (81%) 0.68 [0.40,1.14] 0.46

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Table 7 Multinomial regression analysis to compare respondents’ acceptance towards male Wolbachia-Aedes release and theirperception of the Government’s efforts in controlling dengue

Release site 2_TW Perception of Government’s efforts in controlling dengue

Extremely inadequate/inadequate(Reference)

Neutral*OR (p)

Adequate OR (p) Extremely adequateOR (p)

Acceptance towards maleWolbachia-Aedes release

Very uncomfortable/uncomfortable

6.74 (0.02) 2.01 (0.26) 2.25 (0.37)

Neutral (Reference)

Comfortable 2.41 (0.17) 3.35 (0.0006) 2.14 (0.17)

Very comfortable 0.0004 (0.95) 1.58 (0.52) 12.0 (0.002)

Release site 3_NSE Perception of Government’s efforts in controlling dengue

Extremely inadequate/inadequate(Reference)

Neutral*OR (p)

AdequateOR (p)

Extremely adequateOR (p)

Acceptance towards maleWolbachia-Aedes release

Very uncomfortable/uncomfortable

9.0 (0.03) 1.42 (0.62) 3.0 (0.23)

Neutral (Reference)

Comfortable 1.74 (0.52) 2.79 (0.01) 2.90 (0.09)

Very comfortable 12.0 (0.08) 4.42 (0.18) 12.0 (0.048)

*“Neutral” is taken as reference for acceptance towards male Wolbachia-Aedes release and perception of the Government’s efforts

Table 8 Analysis of socio-demographic factors of respondents at Release site 2_TW and Release site 3_NSE that attribute to highawareness of the dengue situation

Release site 2_TW Release site 3_NSE

High awareness of dengue (feels that dengue is aserious problem/serious problem but under control)

High awareness of dengue (feels thatdengue is a serious problem/seriousproblem but under control)

N Odds Ratio[95% CI]

Odds Ratio[95% CI]

p-value N Odds Ratio[95% CI]

Odds Ratio[95% CI]

p-value

Gender

Male 176 140 (80%) Reference 109 79 (72%) Reference

Female 206 155 (75%) 1.20 [0.87,1.64] 0.57 172 139 (81%) 1.69 [1.18,2.42] 0.14

Age (years)

≤ 35 127 111 (87%) Reference 88 73 (83%) Reference

36–55 98 84 (86%) 2.00 [1.09,3.69] 0.25 86 71 (83%) 1.13 [0.66,1.94] 0.82

> 55 157 100 (64%) 0.33 [0.23,0.49] 0.004 107 74 (69%) 0.41 [0.26,0.64] 0.04

Education level

PSLE and below 139 92 (66%) Reference 109 72 (66%) Reference

‘O’/ ‘A’ - Level or equivalent 132 104 (79%) 1.67 [1.18,2.35] 0.14 88 80 (91%) 4.20 [2.50,7.05] 0.006

Diploma/ Degree/ Postgraduate degree 111 99 (89%) 6.15 [3.54,10.7] 0.001 84 66 (79%) 2.11 [1.38,3.23] 0.08

Perception towards Government’s efforts

Extremely inadequate/ Inadequate 25 18 (72%) Reference 19 15 (79%) Reference

Neutral 53 34 (64%) 0.90 [0.43,1.87] 0.88 48 32 (67%) 2.29 [1.10,4.78] 0.26

Adequate 263 211 (80%) 1.10 [0.58,2.10] 0.88 172 136 (79%) 2.02 [1.10,3.73] 0.25

Extremely adequate 41 32 (78%) 0.66 [0.32,1.39] 0.58 42 35 (83%) 1.33 [0.66,2.68] 0.68

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the Government’s efforts to control dengue in Singaporewere adequate. Studies done in other countries amongurban populations revealed similar high levels ofagreement that dengue is a serious disease, such as inYemen (97.7%) and India (89%) [31, 32]. In the currentstudy, social-demography, such as education level, hadan influence in the level of awareness of dengue amongthe respondents. Therefore, easy-to-remember educa-tional campaigns on dengue prevention would be mostbeneficial in reaching out to this small group of thepopulation who are less educated, narrowing the know-ledge gap in the awareness of dengue. Good knowledgeon the risk of dengue would contribute towards greatermotivation to carry out dengue control measures at theindividual and community levels, as well as for greatersupport towards the Government’s efforts, such as usingWolbachia technology, in controlling dengue. In addition,educational campaigns leveraging the fear element wouldonly be effective if the perceived threat is strong [33].In this paper, we describe a high level of receptivity

towards the use of Wolbachia-Aedes technology as apromising control tool to suppress the Aedes aegyptimosquito vector population in Singapore, gleaned fromthe various public sentiment surveys conducted by theteam. This high level of receptivity may be attributed toa high level of trust felt by the general public towardsthe Government of Singapore. In a recent studyconducted by the Institute of Policy Studies (IPS) SocialLab, a high level of confidence in the Government ofSingapore was reported, ranking second highest amongststudies conducted in 12 other countries [34]. Particularlyin the area of handling public health, it was reportedthat Singaporeans place a lot of trust in, and are satisfiedwith, the Government of Singapore, despite theresometimes being low levels of knowledge in this areaamongst the respondents [35].

Sixty-nine to 88% of the respondents interviewed inthe study had heard of Project Wolbachia – Singapore,with the majority of respondents (32 to 56%) hearing ofthe project through mainstream media (print andbroadcast media) and publicity materials (23 to 33%).Similar findings have also been reported elsewhere,where mass media such as television and newspaperwere identified as the major sources of public healthinformation [36, 37]. However, a survey done inSingapore showed that digital news and social mediaplatforms are growing in popularity due to theconvenience of mobile devices, with majority relying ondigital platforms of key news media for quick, timelyand accurate information [38]. As such, updates on theproject at various key milestones continued to beprovided via various media channels, includingmainstream media, to keep residents well informedabout the progress of the project. Information was alsoregularly made available on the NEA webpage, as well asvia digital and social media platforms.The findings of the surveys reported here should be

cautiously interpreted for several reasons. Although theonline survey was intended for gathering publicperceptions and sentiments towards Project Wolbachia– Singapore, the data gathered was skewed towards theyounger population. A face-to-face street survey wasconducted to complement the online survey, but thesmall sample size may have limited the precision to drawany accurate correlation.Another limitation to consider was administering of

the household perception survey, which was doneduring working hours, when many residents would havebeen at work and thus away from their homes. Thus thehousehold survey done at the study sites may have beenbiased towards residents who were present at homeduring the day, such as homemakers. Nevertheless, the

Table 9 Multinomial regression analysis to compare respondents’ education level and their awareness of dengue

Release site 2_TW Awareness of dengue

Not serious(Reference)

UnsureOR (p)

SeriousOR (p)

Serious but under control OR (p)

Education Level PSLE and below(Reference)

‘O’ or ‘A’ Level 0.93 (0.88) 1.21 (0.64) 2.17 (0.032)

Diploma/Degree/Postgraduate 2.48 (0.18) 4.26 (0.017) 8.45 (0.00015)

Release site 3_NSE Awareness of dengue

Not serious(Reference)

UnsureOR (p)

SeriousOR (p)

Serious but under control OR (p)

Education Level PSLE and below(Reference)

‘O’ or ‘A’ Level 0.88 (0.87) 3.12 (0.045) 6.22 (0.0006)

Diploma/Degree/Postgraduate 1.47 (0.51) 0.71 (0.53) 3.40 (0.006)

“Not serious” is taken as the reference for dengue awareness among respondents. “PSLE and below” is taken as the reference for education level of respondents

Liew et al. BMC Public Health (2021) 21:1417 Page 10 of 12

persons interviewed could actually have most adequatelyrepresented the general sentiments of the public towardsthe release of male Wolbachia-Aedes mosquitoes, as theywould have been the ones most likely experiencing theincrease in number of male Wolbachia-Aedesmosquitoes around their neighbourhoods, since themosquito releases were carried out during the day.As the project progressed, a subsequent survey was

planned, to explore sentiments in greater detail, and tounderstand the knowledge, attitudes and outcomes usingimplicit question types. This would provide anunderstanding of whether there were any changes to thesupport from residents after two years of projectimplementation, and would provide insights on anydifference in perception of the project at newer areas towhich the project was expanded. Understanding ofcommunity perception would help guide subsequenteducational campaigns and publicity.

ConclusionsThe various surveys conducted provided a goodunderstanding of the public acceptance and sentimentstowards the use of Wolbachia-Aedes technology inSingapore. The majority of residents at the study siteshad heard of the ongoing Project Wolbachia –Singapore, involving the novel approach of releasingmale Wolbachia-Aedes mosquitoes, which was atestament to the project team’s efforts in putting outextensive public communications and intensely engagingthe community via a multitude of platforms. Thesurveys also revealed that the majority of the Singaporepopulation recognises the seriousness of dengue,although a small proportion of the community does notperceive the high risk of dengue, which suggests theneed for educational campaigns on the risk of dengue tobe more visual, less wordy, and easier to remember. Asthe project scales up in subsequent phases, there is aneed for longitudinal studies to understand howresidents’ perception and behaviour change over time,and also for in-depth surveys to better identify gaps inthe knowledge and practices related to the prevention ofdengue.

AbbreviationsBH: Braddell Heights; CI: confidence interval; NEA: National EnvironmentAgency; OR: odds ratio; PSLE: Primary School Leaving Examination;TW: Tampines West; NSE: Nee Soon East

AcknowledgementsThe authors would like to thank A/Professor Yung Chee Fu of KK Women’sand Children’s Hospital, and A/Professor Clarence Tam and A/Professor AlexCook of Saw Swee Hock School of Public Health, National University ofSingapore, for their expert advice on survey methodology and analysis. Theauthors additionally thank the student volunteers who helped withconducting the household perception survey.

Authors’ contributionsConceptualisation and study design: CL, LTS, LCN. Data acquisition: CL, LTSand IC. Analysis and manuscript draft: LTS, CL. Manuscript review and editing:CL, LTS, LCN. All authors have read and approved the final manuscript.

FundingThis work was supported by the Ministry of Finance, Singapore under theReinvestment Fund - New approaches in dengue surveillance and control, aspart of National Environment Agency’s feasibility study to determine thepotential of Wolbachia technology as a biological control tool to suppresslocal Aedes aegypti mosquito population.

Availability of data and materialsThe datasets used and/or analysed during the current study are availablefrom the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participateThis study on “Public sentiments towards the use of Wolbachia-Aedestechnology in Singapore” has been submitted for ethical review (throughEnvironmental Health Institute’s management committee, under topsheetTS206). This study was designed to guide public health policies, programmesand actions to prevent and control diseases, and the committee hasdeemed that it falls under the category “Surveillance”, not “Research”, anddoes not require IRB approval.Participation in the study was voluntary, and informed consent was obtainedfrom all participants prior to administration of the surveys, after explainingthe objectives of the study. No personal information or identifier of theparticipants was collected.

Consent for publicationNot applicable.

Competing interestsThe authors declare that they have no competing interests.

Received: 3 April 2021 Accepted: 25 June 2021

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